now to the number one topic burning up our "gma" heat index. It may have been the most anticipated finale ever on "the bachelor." Sean finally finding love and making a dramatic proposal to catherine. The rose. I'll take it. Here's a look at their big moment. &#9834; Looking so crazy in love &#9834; &#9834; will you marry me? Yes. all morning long. Sean, catherine, good morning. Welcome in. So great to meet you. Hi. Nice to see you. Nice to see you again. Thank you very much. Congratulations to both of you. Thank you very much. Long flight. I know it's been a long journey so we thank you for coming to see us this morning. What a -- I mean it's been a whole long story. I just -- did you know early on? I mean how early on did you know? It might -- to the show thinking I'm probably going to know who the top one, maybe two girls are the very first night. But that's -- that wasn't how it happened. Our relationship was slow to progress and then when it did, there came a point where I just knew. I can't see myself saying good-bye to this woman. You seem so nervous in the finale but in your heart, catherine, did you know that it would happen? Yes. Yeah, I did. I mean it's a life-changing moment so obviously I was overcome with emotion. Well, it is an exciting show. A lot of folks were there to see you guys. You know, there's another abc show that oddly is like set up right here. Peta, come here because we're going to make a big announcement. No way. A whole new -- you're adding somebody new. Yes. Is that person in the studio. Oh, no way. Everybody, sean will on "dancing with the stars." Are you kidding me? I'm going to make the transition over to "dancing." Love that show. We love having you back on, by the way. But, wait a minute, how did this happen? How did it happen? We've been keeping this a secret for awhile now. I mean we weren't allowed -- so many secrets. Had you to keep this secret. I am so tired of keeping seeks but now they're all out. That's got to be a relief and now I would imagine you get to get a little training for the first dance. Exactly. Well, that's why I signed up. All in preparation. When we have our big day hopefully I'll make her proud and won't embarrass myself on the dance floor. You did the proposal on the air. You found your woman, your partner on the air. Now you're doing dngz and you're going to have the wedding on tv. We thought it was only fitting. I mean our relationship was created and developed on tv so why not have the wedding on tv, as well. Have you thought, catherine, about what kind of wedding you want it to be? A traditional ceremony but we want to have fun and I know that just our personalities will bring that out anyway so -- all right. I got to talk about the switch, though. You've had zero time to go from that show to a new show that requires an awful lot of practice. Is he going to be ready? Absolutely he's going to be ready. This is going to be one to watch. Can't wait -- so many shows. "The bachelor." "Dancing with the stars." And "dancing with the stars." And the wedding. And the wedding. And more coming up here on "good morning america." Thank you, guys, and

This transcript has been automatically generated and may not be 100% accurate.